Interaction Between Dietary Lipid Level and Seasonal Temperature Changes in Gilthead Sea Bream Sparus aurata: Effects on Growth, Fat Deposition, Plasma Biochemistry, Digestive Enzyme Activity, and Gut Bacterial Community

A 121-day feeding trial was undertaken to test the effects of two dietary lipid levels (16 and 21% L16, L21) in triplicated gilthead sea bream groups (initial weight: 67.5 g) reared at different water temperatures (high, H 23°C low, L 17°C) same recirculation system but exposed a switch temperature after 58 days. Fish kept were transferred (HL transition, autumn shift), fish (LH summer while continuing receive diet apparent satiation each group. At end trial, no significant effect on specific growth rate (SGR), feed intake (FI), conversion (FCR) detected HL transition compared with those LH gross efficiency (GLE) ratio (LER) higher L16. After changes, L16 displayed SGR, FI, GLE, LER, mesenteric fat index reduced. combined low conditions resulted pepsin activity, trypsin, chymotrypsin, lipase activities generally high content. The did not alter metabolic plasma profile, except for observed final aspartate aminotransferase (AST) alkaline phosphatase (ALP) values when combining (L21) changes. Different diets showed significantly gut microbiome layout, only resulting load Lactobacillus . On contrary, impact ecosystem diversity observed, independently from temperature. In addition, favored an increase Weissella Bradyrhizobium genera microbiome, condition L21 Streptococcus Bacillus According results, utilization 16% should be preferred during seasonal changes order optimize health.